1. Field of Invention
The present invention relates to an open-end wrench and, more particularly, to a one-way open-end wrench.
2. Related Prior Art
A conventional open-end wrench includes two jaws extending from a handle. The jaws are engaged with a fastener such as a nut and a head of a screw. The open-end wrench is pivoted to turn the nut or screw for an angle. The jaws are disengaged from the nut or screw. The open-end wrench is returned. This process is repeated for several times so that the nut or screw is tight or slack. The repeating of this process is however troublesome.
As disclosed in U.S. Pat. Nos. 3,695,125, 3,709,073 and 4,158,975, a one-way open-end wrench includes a movable block attached to a first one of two jaws extending from a handle. The movable block and the second jaw are engaged with a nut or screw. The one-way open-end wrench is pivoted in a direction to turn the nut or screw for an angle. The one-way open-end wrench is pivoted in an opposite direction without turning the nut or screw. This process is repeated for several times so that the nut or screw is tight or slack. The first jaw is made with a recess to contain the movable block. The strength of the first jaw is inevitably reduced by the recess. Moreover, it involves a complicated process to make the one-way open-end wrench.
As disclosed in U.S. Pat. No. 7,878,095, a one-way open-end wrench includes two jaws 21 and 22 extending from a handle 10. The jaw 22 is made with a concave arched surface 221 in which a slot 222 is defined. A swing member 23 includes a peripheral protrusion 233 that includes a groove 234.
A spring 26 is placed in the groove 234 before the peripheral protrusion 233 is rotationally placed in the slot 222. A pin 224 is inserted in the groove 234 via apertures 223 defined in the jaw 22. The spring 26 is compressed between a closed end of the groove 234 and the pin 224. Thus, the swing member 23 is returned by the spring 26 placed against the spring 26. With the pin 224, the swing member 23 is retained on the jaw 22 and the strength of the jaw 22 is enhanced. The making of the slot 222 is difficult. Moreover, there is a certain relation between parameters S and H as follows:29% S<H<58% SThe foregoing relation however does not facilitate the sliding of the swing member 23 on the concave arched surface 221 as expected. Moreover, the spring 26 hinders the sliding of the swing member 23 on the concave arched surface 221. Furthermore, it involves a complicated process to make the one-way open-end wrench.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.